This invention relates to a tea processing method. In detail, this is a tea manufacturing method employing firing and rubbing where raw tea leaves are steamed in a firing pot, and infused to yield an aroma inherent to pot firing tea, combined with a taste not having tea harshness characteristic of steam heated tea.
There are two conventional tea manufacturing methods: the steam heating method and the pot firing method. In the former, raw tea leaves are subjected to heated steam to destroy the oxidized enzyme in the tea leaves, after which water drops attached on the surface of the tea leaves are removed. Then they are dried through rough, middle, and fine rubbings to obtain tea leaves of elongated shape. In the latter, raw tea leaves are heated as they are, and the steam generated by the moisture in the raw tea leaves is enclosed with the tea leaves to destroy the oxidized enzyme of the raw tea leaves, eliminate the steam, and infuse the tea leaves.
As to the pot firing method, there are the Aoyagi Method and Ureshino Method. The present inventor has investigated the Ureshino Method. Although this is a sort of pot firing method, it is such that in the initial firing process, a large amount of tea leaves are first agitated and, immediately after the volatilized portion is released, the tea leaves are further agitated to enclose the steam within the tea leaves. This point is called "cross". The high quality of the tea products depends upon treating the tea leaves at high temperature during this "cross" time without scorching. The steam generated by the moisture contained in the tea leaves becomes saturated in the tea leaves to evenly heat the cores of the tea leaves up to about 98 degrees centigrade, resulting in inert oxidized enzyme.
Furthermore, since the inert oxidized enzyme is not caused by saturated steam from the outside, no steam drops attach to the tea leaves, which is different from the steam heating method. In other words, no "mure" takes place, enabling continuous heating.
The present inventor investigated the Ureshino method and invented a manufacturing process disclosed in Japanese Publication of Examined Pat. application No. SH059-46572 and manufacturing equipment described in Japanese Publication of Examined Pat. application No. SH059-27751 and Japanese Publication of Unexamined Pat. application No. SH059-161400.
Afterward, the present inventor further studied how to increase the "cross" temperature. By heating an air-tight firing pot, saturated steam of a higher temperature than steam under atmospheric pressure can be obtained from the moisture in the tea leaves. This saturated steam and residual moisture in the tea leaves get together to produce a high temperature. Thus, the temperature of tea leaves can be increased up to more than 98 degrees centigrade in a short time. It was also found that the steam temperature enables heat to permeate the cores of the tea leaves, resulting in complete inert oxidation enzyme.
More concretely, when tea leaves are heated and fired in a firing pot being oscillated, the firing pot is made air-tight. Consequently, saturated steam at a higher temperature than steam under atmospheric pressure can be obtained by utilizing the moisture contained in the raw tea leaves in the air-tight firing pot. The tea leaves firing method utilizing high temperature steam as well as the residual moisture in the tea leaves was thus discovered. (Japanese Publication of Unexamined Pat. application No. SH062-195248).
However, as a result of succeeding study, the equipment was found to have some inconveniences in actual operation, such as opening and closing of a round disk with a net on the discharge side of the rotary firing pot and air-tight covers, raw tea leaves charging mechanism, heating method, raw tea leaves supply system, fired tea leaves transfer method, and fired tea leaves cooling mechanism.